Stabilized polyolefin compositions containing tin phosphinates



United States Patent 3,296,193 STABILIZED PULYOLEFIN COB POSITIONSCONTAINING TIN PHOSPHINATES Edward N. Walsh, Chicago Heights, 111., andAdam F.

Kopacki, Westwood, NJ., assignors to Staufl'er Chemical Company, NewYork, N.Y., a corporation of Delaware No Drawing. Original applicationAug. 28, 1962, Ser. No. 220,036. Divided and this application Sept. 7,1965, Ser No. 510,722

8 Claims. (Cl. 260-45.75)

This application is a division of copending application 220,036 filed onAugust 28, 1962.

This invention is directed to a novel group of tin phosphinates and thestabilization of polyolefins therewith. In particular, it is concernedwith suppressing the degradation of polyolefins at elevated temperaturesor by prolonged exposure to ultraviolet light by the inclusion in saidpolyolefin of one or more of the novel tin phosphinates disclosedherein. In one preferred aspect of the invention pertains to crystallinepolypropylene compositions stabilized against degradation by havingincorporated therein small amounts of the novel tin phosphinates and tothe methods of preparing said compositions.

The novel compounds of the present invention may be illustrated by thefollowing general formula it [(C H5) 2P YTSIIR 4-m wherein X and Y areselected from the group consisting of sulfur and oxygen, R is selectedfrom the group consisting of phenyl and 1 to 12 carbon alkyl radicals,and m is a positive integer from 1 to 4.

Preparation of the tin phosphinates may be accomplished in accordancewith the following general equation wherein X, Y, R, and m are ashereinbefore defined. Preferably the above reaction is carried out atelevated temperatures in the presence of an organic solvent such asacetone, benzene, and the like. A preferred reaction temperature rangeis between 50 C. and 250 C. The products of the reaction, which arenormally solids (or sometimes viscous liquids), may be separated fromthe reaction matrix by a filtration or decantation. In order to purifythe product it will usually be necessary to remove volatiles underelevated temperatures, wash with water or an organic solvent, and dryunder elevated temperatures and/ or in the presence of a desiccatingagent.

Among the reactants employed by the process of the present invention,the sodium diphenylphosphinodithioate, sodium di-phenylphosphinothioate,and sodium diphenylphosphinate are fairly unknown. However, the parentacids from which these reactants may be prepared are generally known inthe art. In this regard reference is made to Or-ganophosphorusCompounds, Kosolapoff, G. M., John Wiley and Sons Company, Inc., London,1950. Further, typical methods by which these reactants may be preparedare described in the examples which follow hereinafter.

The invention is further illustrated, but not limited, by the followingexamples:

EX M LE 6 5)2 ]2 4 9)2 The (C H P(S)SNa intermediate was first preparedas follows: Into the reaction product of 69.0 grams of sodium in 2liters of 2B ethanol was bubbled H S until the solution was acidic tophenolphthalein indicator. During the H S addition, the temperature washeld below 35 C. Next the reaction mixture was cooled to 0 C.

"ice

and 378.7 grams of (C H P(S)C1 was added dropwise while stirring over aperiod of one hour. When the slightly exothermic reaction and theprecipitation of NaCl ceased, the mixture was stirred further for onehour (0 C.), then warmed slowly to 45 C., held for 30 minutes, cooled,and finally, filtered. The filtrate was concentrated by stripping offsolvent and the product was fractionally crystallized (fromether-ethanol solution) to furnish a yield of sodiumdiphenylphosphinodithioate.

Thirty grams of Sn(C H Cl in 150 ml. of acetone was then added to 55.0grams of the sodium diphenylphosphinodithioate inter-mediate prepared bythe foregoing method. The reaction mixture was refluxed for 3 hours andfiltered. The filter cake was washed with 500 ml. of H 0 and air driedto yield 58.5 grams (80% yield) of S,S-bis(diphenylphosphinodithio)dibutyl tin having a melting point range of l38140 C. and an analysis of8.4% P, 17.8% S, and 15.1% Sn compared to the theoretical calculatedvalues for the product of 8.4% P, 17.5% S, and 16.3% Sn.

The (C H P(O)SNa intermediate was first prepared as follows: To asolution of 250 ml. of concentrated HCl in 200 ml. H O was addeddropwise 130.0 grams of (C H P(S)Cl while stirring at refluxtemperature. Thereafter the reaction mixture was stirred at reflux for 2additional hours, cooled, and the resulting crystalline product, whichanalysed as (C H P(O)SH (94% of theoretically predicted yield) having amelting point of 148-150 C., was recovered by filtration and dried. To asolution prepared by reacting 9.9 grams of Na with 300 ml. ethanol wasadded grams of the (C H P(O)SH produced from the foregoing reaction. Themixture was slowly warmed to reflux and an exothermic reaction wasobserved. After this reaction subsided the solvent was stripped from themixture yielding 108.5 grams of sodium diphenylphosphinothioate with amelting point of 260 C.

To 25.6 grams of sodium diphenylphosphinothioate in 150 cc. of acetonewas added 15.2 grams of Sn(C H Cl The mixture was refluxed for threehours, cooled, and poured into ice water. The oil layer was extractedwith ether, washed with 100 cc. each of 4% NaOH and Water, and counterwashed with ether (100 cc.). After drying the washed solution over Na SOthe ether was stripped from the product at 60 C./1 mm. Hg to yield 30.0grams (86% of calculated yield) of S,S-bis (diphenylphosphinothio)dibutyl tin having an index of refraction N :1.6275. The analysis showed8.8% P, 9.4% S, 0.6% Cl and 16.4% Sn compared to 8.9% P, 9.2% S, 0.0% Cland 17.0% Sn, theoretical.

The (C H P(O)ONa intermediate was first prepared as follows: To asolution of 250ml. of concentrated HCl in 200 ml. of H 0 was added 130.7grams of while stirring at reflux. After one additional hour at refluxthe solution was cooled whereupon (C H P(O)OH crystallized out ofsolution and was recovered and dried. To a solution consisting of 48.5grams of the in 100 ml. H O was added sufficient NaOH (50% solution) toeffect neutralization. The water was removed by heating the solutionunder vacuum to furnish an essentially qualitative yield of sodiumdiphenylphosphinate.

To 9.8 grams of sodium diphenylphosphinate in 75 ml. of acetone wasadded 6.1 grams of Sn(C H Cl The mixture was refluxed for three hours,poured into 500 ml. of ice water, and filtered. The filter cake wasrinsed with 3 500 ml. of water, then with ethyl ether, and finally,dried to 60 C. at 1 mm. Hg. Analysis of the product (13.0 grams, 98%yield) showed 9.3% P, 18.9% Sn, and 0.0% Cl compared to the calculatedvalues of 9.6% P, 17.8% Sn, and 0.0% Cl for 0,0-bis(diphenylphosphino)dibutyl tin.

EXAMPLE 4.[(C H P(S)S]4,Sn

To 5.2 grams of SnCl, in 100 ml. acetone was added 22.0 grams of sodiumdiphenylphosphinodithioate (prepared in accordance with the methoddescribed in Example 1). The solution was refluxed for three hours thenpoured into ice water and filtered. The filter cake was dried to yield19.4 grams (80% yield) of S,S,S,S-tetra (diphenylphosphinodithio) tin.By analysis the product contained 10.7% P, 23.1% S, and 11.0% Sncompared to the theoretical calculated values of 11.1% P, 23.2% S, and10.7% Sn.

Nine grams of sodium diphenylphosphinodithioate (prepared by method ofExample 1) was added to 11.5 grams of Sn(C H Cl in 100 ml. acetone. Thesolution was refluxed for six hours, cooled, poured into ice water, andextracted with ether and benzene. The solution was thereafter dried overNa SO and the volatiles were re moved at 60 C. and 1 mm. Hg. Uponanalysis the product (18.0 grams, 100% yield) was found to contain 6.0%P, 10.8% S, and 17.4% Sn compared to the calculated values of 5.2% P,10.7% S, and 19.8% Sn for the compound S-diphenylphosphinothio-triphenyltin. The melting point was 127-130 C.

The following specific compounds were prepared by methods substantiallyin accordance with one or more of those described in Examples 1 through5, which methods employed the substituted or unsubstituted tin chloridesand sodium diphenylphosphinodithioate, sodium diphenylphosphinothioate,or sodium diphenylphosphinate that would indicate by the structure ofthe resulting product. Where significant and/ or available, typicalyields and analyses are furnished.

S,S-bis(diphenylphosphinodithio) diphenyl tin; M.P.= 218220 C.;yield=96.2% of theory. Analysis. Found: 8.2% P, 15.6% S, 16.9% Sn.Calculated: 8.1% P, 16.6% S, 15.4% Sn.

'of theory. Analysis.Found: 7.3% P, 12.4% Sn. Ca1- culated: 7.0% P,13.3% Sn.

0,0-bis(diphenylphosphino) diphenyl tin; yield=89% of theory.

S,S,S,S-tetra(diphenylphosphinothio) tin; yield- -61% of theory.Analysis.-Found: 11.0% P, 11.2% S, 11.2% Sn. Calculated: 11.8% P, 12.2%S, 11.3% Sn.

forced draft oven to a temperature of 150 C., a one inch diameter discabout 25-30 mils thick, prepared from unstabilized polypropylene, willnormally become brittle or disintegrate within a period of one or twohours. Generally, all of the known grades of polyolefins are more orless subject to air oxidation as above described, al-

though the crystalline or stereo-regular polypropylene is especiallyprone to this phenomenon.

Likewise, the polyolefins (and in particular polypropylene) undergodegradation at more moderate temperatures when exposed to ultravioletlight for long periods of time. For example, polypropylene discs of thesize described hereinbefore will usually become brittle within about-110 hours when exposed in an Atlas Weatherometer: (xenon arc type withwater spray) at a temperature of.

Obviously, polypropylene requires stabilization against oxidative andultraviolet light degradation, and numerous varieties of additives havebeen proposed in an effort to suppress these undesirable features.mercial additives suggested for this purpose are the bis (dialkylphenol)sulfides, including monosulfides and disulfides. The following tableillustrates typical test data on crystalline polypropylene stabilizedwith 0.5% of the indicated prior art bis phenolic sulfide anti-oxidant.Each polypropylene test sample was exposed in a forced draft oven to atemperature of C.

Table 1 Compound: Time to embrittlement, hours 4,4'-thiobis(6-tert-butyl-o-cresol) 38 2,2'-thiobis (4-methyl-6-tert-butylphenol).16 4,4'-thiobis (6-tert-butyl-m-cresol) 78 Many highly effectivecompounds are presently available for stabilizing polypropylene againstweathering (U.V.) degradation. The following table illustrates thestabilizing elfect of various typical commercial polypropyleneultraviolet light stabilizers (0.5 of the total resin) when tested in anAtlas Weatherometer at a tempenature of 140 F.

Table II Compound: Time to embrittlement, hours Z-hydroxy 4-methoxy2-carboxy benzophenol 750 2 (2' hydroxy 5'-methyl phenyl) benzotriazole336.5. 2-hydroxy 4-methoxy benzophenone 468 Octyl phenyl salicylate 5072-hydroxy 4-n-octoxy benzophenone 2107 Among the com.

Unfortunately, commercial ultraviolet light absorbers normally havelittle or no activity as anti-oxidants. For example, unstabilizedpolypropylene containing any of the compounds shown in Table II willbecome brittle within about four hours by the forced draft oven test 150C.). In most cases failure will be observed in about two hours.

The novel tin phosphinates of the present invention, and in particularthe dithio compounds, have been found to inhibit degradation (oxidativeand/or ultraviolet) of polyethylene, polypropylene, and polybutylene.Further, the degree of stability accomplished is generally equal to orsuperior to the prior art stabilizers. For oxidation or heat stabilitythe tin phosphinates may be added in concentrations of between 0.05% and0.5% by weight of the total polymer composition. Somewhat higherconcentrations are normally required for ultraviolet lightstabilization. The preferred concentration for ultraviolet lightstabilization is between 0.5% and 2.0% by weight of the final polymer,and in essentially all cases not less than 0.1% nor more than 5.0% byweight of the composition. The following table summarizes the resultsobtained by testing crystalline polypropylene compositions containingthe novel compounds of the invention, at the concentra tions indicated.

T able, III

Time to Embrittlement, hours Compound Oxidation (Forced Draft Oven at150 0.)

UV. Absorption (Atlas Weatherometer at 140 F.)

S-diphenylphosphinodithio triphenyl From the data of Table III it may beobserved that a mixture of 0,0-bis(diphenylphosphino) dibutyl tin anddilaurylthiodipropionate is synergistic in stabilizing polypropylene toheat degradation. Such synergism has been observed with other compoundsof the invention on both oxidative degradation and ultraviolet lightdegradation.

It has been found generally that the phosphinodithio compounds of thegeneral formula wherein R and m are as previously defined, are moreeflicient than the phosphinothio and phosphino compounds in stabilizingcrystalline polypropylene, and, for this reason, the phosphinodithiocompounds represent a preferred class of polypropylene stabilizers.

The following example illustrates the procedure for preparing stabilizedcrystalline polypropylene compositions of the invention, although theinclusion of this example is not to be taken as limiting or otherwiseimposing any restrictions on the invention and it is understood thatvariations in practicing the same without departing from the scope orspirit thereof will be apparent to those skilled in the art to which thesaid invention pertains.

EXAMPLE 17 Ten grams of powdered polypropylene resin containing 0.5% ofthe selected candidate stabilizer was placed on the center of a 6" x 6"stainless steel plate. A similar steel plate was then placed on top ofthe powder while exerting a slight downward pressure. The assembly wasplaced in the center of the lower platen of a hydraulic press which waspreviously heated to 350 F. The lower platen of the press was raiseduntil both platens contacted the upper and lower 6" x 6" steel plates.The powdered sample was allowed to warm up for about 4 minutes or untilfusion of the resins occurred. As the resin began to melt, the lowerplaten of the press was raised slightly to insure that both platenscontacted the steel plates enclosing the sample. After about 4 minutesor when the fusion of the resin occurred, the lower platen was raised toa one-ton load and so maintained for tWo minutes. The drain valve wasthen opened to vent on steam, after which cold Water was admitted tocool the platen and plates to 50 F. The molded circular sheet of resinwas approximately 25-30 mils thick.

One inch discs were cut from the molded sheet and placed in petri dishesand then exposed to a temperature of 150 C. in a forced draft oven. Thesamples were examined periodically and checked for signs ofdiscoloration, crystallization, opacity, scorching of the edges,complete embrittlement and cracking. After removal from the oven, the'samples were then compared with control samples containing nostabilizer. For determining the stability to ultraviolet light the 1"discs were placed in an accelerated, artificial weathering apparatus(Atlas Weatherometer) containing a xenon arc and a water spray andmaintaining a temperature of F. The water was sprayed upon the discs for18 minutes during every two hours of test time. The test discs wereperiodically examined to determine the point of gross embrittlement. Theresults obtained by the use of the various tin phosphinates of theinvention are summarized in Table III, supra.

The mixture of powdered propylene resins and stabilizer as used in theabove described procedure was prepared by intimately comingling thepropylene resin and the stabilizer in a Waring Blendor until ahomogenous mixture of the components was obtained. The polypropyleneresin was an unstabilized, general-purpose high molecular weightpolypropylene resin of the isotactic or crystalline type. A typicalisotactic resin as above described has a melt index of 4 at 230 C. and aspecific gravity of 0.905. An example of this type of polypropyleneresin is commercially available under the trade name Profax 6501, typeP02004, and is supplied in the form of natural flakes. Othercommercially available grades of unstabilized isotactic polypropyleneresins have been used, and in this connection, mention is made of:

(1) Unstabilized Avisun Polypropylene (Avisun Corporation).

(2) Unstabilized Escon Polypropylene (Enjay Chemical Company).

The foregoing detailed description is given for clearness ofunderstanding only and no unnecessary limitations should be impliedtherefrom.

We claim:

1. A stabilized polyolefin composition comprising a polymer obtained bypolymerizing at least one unsaturated mono-olefinic hydrocarbon monomerof 2 to 4 carbon atoms and from 0.05 to 5.0 percent by weight of thetotal polymer composition of a compound of the formula II 0 H PY-SnR a92 Jm 4 wherein X and Y are selected from the group consisting of sulfurand oxygen, R is selected from the group consisting of phenyl and 1 to12 carbon alkyl radicals, and m is a positive integer from. 1 to 4.

2. The polyolefin compositions of claim 1 wherein the compound of theformula is added in an amount of from 0.5 to 2.0 percent by weight basedon the weight of the total polymer compositions.

wherein R is selected from the group consisting of phenyl and 1 to 12carbon alkyl radicals and m is a positive integer from 1 to 4.

4. A stabilized polypropylene composition comprising polypropylenehaving a high degree of crystallinity and as a stabilizer therefor from0.05 to 5.0 percent by Weight of the total polymer composition ofS-diphenylphosphinodithio triphenyl' tin.

5. A stabilized polypropylene composition comprising polypropylenehaving a high degree of crystallinity and as a stabilizer therefor from0.05 to 5.0 percent by weight of the total polymer composition ofS,S-bis(diphenylphosphinodithio) dilauryl tin.

6. A stabilized polypropylene composition comprising polypropylenehaving a high degree of crystallinity and as a stabilizer therefor from0.05 to 5 .0 percent by weight of the total polymer composition ofS,S-bis(diphenylphosphinodithio) dioctyl tin.

7. A stabilized polypropylene composition comprising polypropylenehaving a high degree of crystallinity and as a stabilizer therefor from005 to 5.0 percent by weight of the total polymer composition ofS,S-bis(diphenylphosphinodithio) dibutyl tin.

8. A stabilized polyolefin composition comprising ;a polymer obtained bypolymerizing at least one unsaturated mono-olefinic hydrocarbon monomerof 2 to 4 carbon atoms, from 0.05 to 5.0 percent by weight of the totalpolymer composition of a compound of the formula:

II C H PY-SnR -m a 5): Jm 4 wherein X and Y are selected from the groupconsisting of sulfur and oxygen, R is selected from the group consistingof phenyl and 1 to 12 carbon alkyl radicals, and m is a positive integerfrom 1 to 4, and a dilaurylthiodi: propionate.

References Cited by the Examiner UNITED STATES PATENTS 2,735,836 2/1956Tanning 260 -4575 2,906,731 9/1959 Hill et a1. 260-4575 3,055,925 9/1962Hartle 260-429 LEON I. BERCOVITZ, Primary Examiner.

G. W. RAUCHFUSS, Assistant Examiner.

1. A STABILIZED POLYOLEFIN COMPOSITION COMPRISING A POLYMER OBTAINED BYPOLYMERIZATION AT LEAST ONE UNSATURATED MONO-OLEFIN HYDROCARBON MONOMEROF 2 TO 4 CARBON ATOMS AND FROM 0.05 TO 5.0 PERCENT BY WEIGHT OF THETOTAL POLYMER COMPOSITION OF A COMPOUND OF HTE FORMULA